Interactive Transcript
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I'm here with my young, brilliant colleague,
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Dr. Ben Laser,
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and we are looking at a 48-year-old lady
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with some visual problems
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and those visual problems are on which side?
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Little scrolling here and hopefully you figured out
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within a matter of seconds
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that the visual problems are on the left,
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the patient's left or our right.
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The optic nerve looks like a big tube.
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So, one of the challenges that we have
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in a case like this,
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I'll use my drawing tool,
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is with this sort of fusiform enlargement,
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and this is what I mean by fusiform.
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Are we looking at something
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that is intrinsically expanded?
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Or conversely, are we looking at something
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where we have an optic nerve
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and around the optic nerve,
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we've got something sitting around it
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and it's all kind of blending together
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on this pulsing sequence
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which is water weighted,
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but it's not a true T2-weighted image.
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It's more of a steady state free procession,
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which doesn't have terrific contrast resolution.
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So the answer is
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it's very hard to tell on this sequence.
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So, if you're going to make a judgment right here
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you're probably going to come up on the short end
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or you're going to have to guess.
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But we don't guess
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in radiology, we use other pulsing sequences.
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So, what would you do?
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A post-contrast would probably be the best
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sequence to look at
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the characteristics of the lesion.
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And what plane would you use?
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I would either look at a sagittal or
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if you can do an oblique sagittal
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to kind of look through parallel with the orbit.
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So, a lot of people do this
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and that's because they can
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and not everybody can go oblique,
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but most people these days can go oblique.
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And so,
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if you can go oblique, you absolutely should.
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And let's show you what we mean by that.
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So, we're going to go oblique.
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We're going to go absolutely
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balls on parallel to the optic nerve.
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And when we do that,
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this is what we get.
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So, these are both contrast-enhanced oblique images.
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This one over here is the right side,
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this one over here is the left side,
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so this one is on the right orbit
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or optic nerve
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and this one is the left orbit and optic nerve.
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Now the right one, pretty clear-cut.
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We see the optic nerve, this gray structure,
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and some dura around it.
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That's dark, maybe exacerbated a little bit
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or made more conspicuous by some magic angle effect,
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and the CSF, you don't see very well.
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even though there is a little bit of CSF around there
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because it's a T1.
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So, the CSF is going to be kind of dark,
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so that's not visible right now.
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Did a T2, you'd see a little
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thin stripe of high signal around the optic nerve.
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When we go to the abnormal nerve,
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you gotta look at it.
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You gotta really have a little bit of creativity here.
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You gotta say to yourself,
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"Okay, let's do a little scrolling."
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Is this thing that I see,
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this fluffy, irregular, hyperintense enhancing thing,
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is it inside the nerve, blowing the nerve out?
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Or is it around the nerve
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making the margins of the nerve rather fuzzy?
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If you look very carefully,
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there is the nerve right there.
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I'm gonna make it even bigger.
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That's the nerve right there.
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That is a little bit of dural tissue on either side.
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The rest of the tissue around that,
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including this bulky tissue underneath,
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there's a little more of the nerve. Right there.
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There is the nerve,
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there is the tissue around it.
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So, it is a little tram-tracky.
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In other words, what I mean by that is
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you've got the nerve,
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although it's kind of irregular
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now cause it's getting pushed around
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and sometimes it'll
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it'll form what's called the dotted eye sign.
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You know it becomes kind of irregular
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and then is punctuated
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at the very end where it inserts on the sclera.
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So you got the nerve,
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but then around the nerve,
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here's the nerve right there,
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around the nerve, you have this mushy,
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irregular enhancing tissue,
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which I'll make aquamarine blue,
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and you can see it's a little more bulky inferiorly.
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Right there.
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And so the answer in this case is meningioma.
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Another reason that meningioma would be favored here is,
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you look at the T2-weighted image,
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and I believe we have a regular T2 here somewhere.
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Let's see if we've got it.
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We do.
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And you look at this lesion,
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you know an optic nerve glioma,
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you'd like them to have a little bit of heterogeneity, right?
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It's a glioma.
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You know.
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They're not an ordinary bright,
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but this one's like totally grey,
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just like a meningioma would be.
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Kind of smooth gray,
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only slightly heterogeneous lesion.
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So, it's got the perfect
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T2 signal intensity
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on a T2-weighted image for a meningioma,
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much better than it does for a chiasmatic
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or optic nerve glioma.
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What percent of individuals that
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have optic nerve glioma have enough one?
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It's about 15%.
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About that. Yeah, 15 to 20.
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Yeah, 15 to 20.
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And then the converse,
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you know people with NF1 who have optic nerve gliomas,
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a lot of them have pilocytic astro dysplasia,
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the optic pathway.
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And in my experience,
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it's somewhere between 15 and 30%
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will eventually develop some form of
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optic nerve glioma.
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So, this is an optic nerve glioma.
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It looks like it gets back close to the apex.
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We have a matching case that came from the
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from the brain and grew into the apex.
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This one probably came
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directly from the sheath of the optic nerve
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and is growing
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out the back, towards the apex.
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Let's move on, shall we?
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